Field
Aspects of the present invention generally relate to power control of an image forming apparatus.
Description of the Related Art
In recent years, amid growing environmental awareness, attempts have been made to save power of image forming apparatuses such as copying machines. For example, when an apparatus is not used for a predetermined time, or when a user instructs a shift to a low power consumption state (i.e., sleep mode), the apparatus is shifted to the sleep mode to save the power. This sleep mode is provided to achieve power saving by stopping power supply to, for example, a printer unit and a scanner unit.
However, when using the apparatus shifted to the sleep mode, the user needs to press a button to return the apparatus from the sleep mode or needs to wait some time to use the apparatus after pressing the button, which is less convenient for the user. To address this situation, image forming apparatuses with sensors have appeared. This type of image forming apparatus includes a human body detection sensor such as an infrared sensor and a capacitance sensor, and returns from a sleep mode by detecting proximity of a user to the apparatus.
However, depending on the type or usage of the human body detection sensor, the human body detection sensor causes a return by erroneously detecting the user in some cases. For example, in a case where the apparatus is installed at a passage, a return from sleep occurs when the sensor detects a person merely passing by the apparatus, as a user. To prevent this situation, it is conceivable to reduce a detection range of the human body detection sensor, so that the apparatus returns from sleep only when a user stands extremely close to the apparatus. However, in this solution, the user may stand at a position falling outside the detection range or a return from sleep may take a longer time due to a delay in user detection, which is less convenient.
In this connection, one technique has been discussed as follows. This technique detects a human body with a human body detection sensor driven by time division. The presence of the human body is determined when a human body detection signal is continuously output from the human body detection sensor only during a predetermined time interval. When this determination is made, a return from a sleep mode occurs (see Japanese Patent Application Laid-Open No. 2002-71833). According to the technique in Japanese Patent Application Laid-Open No. 2002-71833, a human body is determined to be a user, when being in proximity to the human body detection sensor for more than a given time period. Therefore, it is possible to prevent an unintended return from a sleep mode, without reducing a detection range of the human body detection sensor.
However, in the above-described conventional technique, when a user approaches and then stops in front of an image forming apparatus to take a sheet output from this apparatus, the user is assumed to be a human body present in proximity to the sensor for a predetermined time. Therefore, a return from the sleep mode occurs. On the other hand, when a user who desires to immediately use the image forming apparatus approaches, the user needs to wait for the predetermined time, which is less convenient.